Highly scalable acid-base resistant Cu-Prussian blue metal-organic framework for C2H2/C2H4, biogas, and flue gas separations

Abstract

One of the emerging problems plaguing the chemical industry today is the selective capture and separation of gases from their mixtures in an efficient and cost-effective manner. MOFs are new-age physisorbent materials extensively investigated for various gas mixture separations (such as biogas, flue gas, olefin/paraffin etc.); however, face the challenge of separations in a realistic environment. Here, we have investigated one of the Prussian blue analogues (Cu-PSB) to explore its potential as energy-efficient gas separation material. Cu-PSB can easily be scaled up at room temperature from water and is highly robust under harsh acidic, basic environments (pH = 1–11, 6 M HCl, 18 M H2SO4), exhibiting excellent separation of C2H2/C2H4, biogas (CO2:CH4 = 50:50), and flue gas (CO2:N2 = 15:85) mixtures. The IAST selectivity at ambient conditions (295 K, 50:50 mixture) could reach up to 5.2 for C2H2/C2H4, 14.7 for CO2/CH4, and 60.5 for the CO2/N2 (15:85 mixture). Such high C2H2 and CO2 uptake capacity and separation selectivity could be attributed to the synergistic effect of open CuII sites and the multiple H-bonding interactions within the functional pore channels of optimal pore size. Further, breakthrough simulation confirmed the complete separations from their binary mixtures, thus proving to be highly useful for the C2H2/C2H4 separation and CO2 capture from the bio and post-combustion flue gas mixtures. Cu-PSB was found to be even a more robust framework than ZIF-8 and UiO-66 MOFs.